Split gain transfer function for smart motor actuators

ABSTRACT

The present disclosure relates to systems and methods for controlling the operation of a motor actuator for positioning a moveable element. Operational characteristics of the movable element over its operational range are determined. A first PWM signal to control the actuator over a first portion of the operational range of the movable element is generated. A second PWM signal to control the actuator over a second portion of the operational range of the movable element is generated. The first PWM signal is based on a linear transfer function having a first gain level and the second PWM signal is based on a linear transfer function having a second gain level. An output position of the moveable element is executed based the first PWM signal or the second PWM signal.

BACKGROUND

The present disclosure relates to the operation of an actuator system.More particularly, but not exclusively, the present disclosure relatesto using a multi-gain transfer function for greater control in operatinga motor actuator.

SUMMARY

Actuators, such as smart motor actuators, are well known in the field ofelectromechanics as a component of a machine that moves or controls amechanism or system. Fundamentally, in order to operate, actuatorsrequire control signals and a source of energy. Actuators receivecontrol signals and react by converting the source's energy intomechanical motion, such as torque, e.g., in order to introduce motion aswell as to prevent it. Therefore, actuators can be used in variousapplications, such as industrial manufacturing systems, engine controlsystems and robotics.

The control signals used for operating an actuator can be an electricvoltage, for example using Pulse-Width Modulator (PWM) signals,otherwise described as drive signals, and the main source of energy maybe an electric current. The main motivation of using PWM signals as thecontrol signal for actuators and motor actuator systems is due to itsenergy and power efficiency, and high precision along with noiseimmunity, in comparison to an analog signal.

A smart motor actuator can be defined as an integrated actuator systemcomprising several components. Smart motor actuators generally comprisea control unit and an actuator, the actuator having, for example, a D.C.motor, a gearbox, an output shaft and a coupled feedback sensor. Smartmotor actuators are widely used across industries, particularly inengine control systems such as in the application of Exhaust GasRecirculation (EGR) valves, wastegate actuators and exhaust gas controlvalves, for example.

Typically, smart motor actuators can be controlled mechanically orelectronically, software-driven or human-operated, and mechanisms andsystems can be operated with efficiency using communication linesbetween component parts which has resulted in an increase in demand forsmart motor actuators across industries.

Actuators implement controllers that, when in communication with acontrol unit, receives signals or commands and returns diagnosticmessages or other feedback data in relation to the actuator. The controlunit commonly communicates with the actuator via the controller using aPWM communication line. In this way, the control signal can be both sentto and detected reliably and accurately at the controller. It is alsoknown that similar communication schemes are also used in systems ofpump control, such as auxiliary water pumps and fuel pumps, for example.

Actuator motors typically have a variable positional output rangebetween 0% and 100%, whereas the pulse-width modulator does not use thefull range of its commands, for example, at the lower and upper commandlimits, as they are indistinguishable from short to ground, short tobattery or open circuit, as it would be understood by the skilledperson.

Existing actuators, particularly smart motor actuators, operate using asingle gain transfer function that defines the distribution of the PWMcommand range over the operational range of the actuator motor, in orderto form a relationship between each PWM command and an output positionof the motor. Typically, when using a single gain transfer function, thePWM may accept commands having a resolution of 1%. In other words, forevery 1% increase in the PWM command the output position of the motorincreases consistently at a rate, otherwise described as a gain level orfactor, greater than 1%.

A single gain transfer function can result in a non-linear correlationbetween the PWM signals and the output positions of the motor.Therefore, motors operated by single gain transfer functions may not becapable of achieving certain target positions. The result is adiscontinuity with respect to the positional increments that can beachieved by the motor.

Particularly, in applications where a more accurate or effective levelof control is required, the lack of control over the positional range ofthe motor is not ideal and the ineffectiveness can often result infaults in the system, particularly where greater control is necessary.

In view of the foregoing, the present disclosure provides methods foroperating a motor actuator and systems thereof.

In accordance with a first aspect of the disclosure, there is provided amethod of operating an actuator for positioning a movable element. Themethod comprises determining operational characteristics of the movableelement over its operational range, e.g., the operational range ofmotion of a valve. The method may further comprise generating a firstPWM signal to control the actuator over a first portion of theoperational range of the movable element, e.g., to control a firstportion of the operational range that requires a lower degree ofaccuracy. The method may further comprise generating a second PWM signalto control the actuator over a second portion of the operational rangeof the movable element, e.g., to control a second portion of theoperational range that requires a greater degree of accuracy. The firstPWM signal can be based on a linear transfer function having a firstgain level and the second PWM signal can be based on a linear transferfunction having a second gain level. The method further comprisesexecuting an output position of the moveable element based the first PWMsignal or the second PWM signal, e.g., to achieve a target or desiredpositional output of the moveable element of the actuator.

The present disclosure results in a method that maintains overall powerefficiency whilst increasing the level of control over the operationalrange of the actuator motor where required, thus providing a moreeffective method for operation that compensates for the inaccuraciesthat occur in existing methods of actuator operation that implement asingle gain level. More particularly, by way of various examplesdescribed herein, the present disclosure seeks to overcome thelimitations of existing actuator systems and methods of operating suchsystems by using a split gain transfer function.

In some variations, the first PWM signal is generated based on thedetermined operational characteristics of the moveable element at thefirst portion of its operational range and the second PWM signal isgenerated based on the determined operational characteristics of themoveable element at the second portion of its operational range.

The method disclosed herein implement a multi-gain transfer functionhaving at least two gain levels that can be used to control differentportions of the operational range of the moveable element, otherwisedescribed as a piecewise linear transfer function, a split gain transferfunction or as two or more separate linear transfer functions. E.g., theactuator may be operated with a power efficient PWM mechanism at someportions of the operational range of the moveable element, whereinaccuracies are or may be allowed, whilst implementing a lower gainlevel at other portions of the operational range where it may bedesirable to output motor positions a greater degree of accuracy orprecision.

In some variations, the first gain level and the second gain level eachindicate a ratio between the operational range of the moveable elementand a PWM range.

In some variations, wherein at least one of the first PWM signal and thesecond PWM signal is further generated to control the actuator over oneor more additional portions of the operational range of the movableelement. E.g., depending on the application or the operationalcharacteristics of the moveable element, it may be desired to gaingreater control of the moveable element's output at the start and endportions of its operational range.

In some variations, the first gain level is greater than 1 and thesecond gain level is equal to 1. E.g., it may be desirable in someapplications to have at least one gain level set to have a factor of 1in order to access all output positions or increments available withinthe operational range of the motor.

In some variations, the method further comprises a step of receivingfeedback data in relation to the moveable element from a feedback sensorcoupled to the actuator. Feedback data can be communicated back to thecontrol unit, where the control unit may respond with updated PWMcommands to compensate for any internal losses incurred, for example,impacting the output position of the moveable element.

In some variations, the method further comprises a step of adjusting atleast one of the first PWM signal and the second PWM signal in responseto the feedback data. Using feedback data, the PWM command or PWM signalcan be corrected or adjusted, e.g. dynamically or substantiallyinstantaneously, to react with a more accurate gain level in order toachieve the desired output positions more effectively.

In some variations, the step of adjusting the at least one of the firstPWM signal and second PWM signal is based on one or more vehicleparameters.

According to a second aspect, there is provided an actuator controlsystem. The actuator control system comprises a control unit incommunication with an actuator comprising a moveable element, thecontrol unit being configured to drive the actuator. The actuatorcontrol system may further comprise means for determining operationalcharacteristics of the movable element over its operational range. Theactuator control system may further comprise means for generating afirst PWM signal to control the actuator over a first portion of theoperational range of the movable element, e.g., to control a firstportion of the operational range that requires a lower degree ofaccuracy. The actuator control system may further comprise means forgenerating a second PWM signal to control the actuator over a secondportion of the operational range of the movable element, e.g., tocontrol a second portion of the operational range that requires agreater degree of accuracy. The first PWM signal may be based on alinear transfer function having a first gain level and the second PWMsignal may be based on a linear transfer function having a second gainlevel. The actuator control system further comprises means for executingan output position of the moveable element based on the first PWM signalor the second PWM signal, e.g., to achieve a target or desiredpositional output of the moveable element of the actuator.

According to a third aspect, there is provided a vehicle comprising atleast one of the actuator control systems according to the secondaspect.

According to a fourth aspect, there is provided a non-transitorycomputer readable medium having instructions encoded thereon that whenexecuted by control circuitry cause the control circuitry to determineoperational characteristics of the movable element over its operationalrange, e.g., the operational range of motion of a valve. The controlcircuitry may be further configured to generate a first PWM signal tocontrol the actuator over a first portion of the operational range ofthe movable element, e.g., to control a first portion of the operationalrange that requires a lower degree of accuracy. The control circuitrymay be further configured to generate a second PWM signal to control theactuator over a second portion of the operational range of the movableelement, e.g., to control a second portion of the operational range thatrequires a greater degree of accuracy. The first PWM signal may be basedon a linear transfer function having a first gain level and the secondPWM signal may be based on a linear transfer function having a secondgain level. The control circuitry is further configured to execute anoutput position of the moveable element based the first PWM signal orthe second PWM signal, e.g., to achieve a target or desired positionaloutput of the moveable element of the actuator.

According to another aspect, there is provided a method of operating anactuator comprising a moveable element. The method comprises generatinga PWM signal based on a linear transfer function having a first gain anda second gain.

It should be appreciated that other features, aspects and variations ofthe present invention will be apparent from the disclosure herein of thedrawings and detailed description. Additionally, it will be furtherappreciated that additional or alternative examples of methods of andsystems for operating actuators may be implemented within the principlesset out by the present disclosure.

FIGURES

The above and other objects and advantages of the disclosure will beapparent upon consideration of the following detailed description, takenin conjunction with the accompanying drawings, in which:

FIG. 1 illustrates a circuit diagram for an actuator system inaccordance with example examples of the present disclosure.

FIG. 2 shows an example graph depicting the relationship between thecommanded output positions and the actual output positions of the motorusing a single gain transfer function.

FIG. 3 shows an illustration of the signal losses at edges of the PWMduty cycle due over time.

FIG. 4 shows a graph illustrating an example piecewise transfer functiondepicting a change in the positional output of the motor over the fullrange of PWM commands using a multi-gain transfer function.

FIG. 5 shows a plotted view of the example piecewise transfer functionthat has been modelled according FIG. 4 .

FIG. 6 shows an exploded view of the linear gain level portion as shownin FIG. 5 .

FIG. 7 is a schematic showing a vehicle comprising an exemplary actuatorcontrol system, in accordance with some examples of the disclosure.

FIG. 8 is a block diagram showing exemplary control circuitry, inaccordance with some examples of the disclosure.

The figures herein depict various examples of the disclosure's inventionfor purposes of illustration only. It shall be appreciated thatadditional or alternative structures, systems and methods may beimplemented within the principles set out by the present disclosure.

DETAILED DESCRIPTION

With reference to FIG. 1 , an example structure of an actuator system100 of the present disclosure will now be described.

In the example of FIG. 1 , an actuator system 100, or smart motoractuator system, is an integrated actuator 104 and control unit 102system comprising several components including, but not limited to, amotor (A.C. or D.C.) 110, an output shaft (linear or rotary) 112, acontroller 106 such as a microcontroller, gears 114 or gearboxes,sensors or feedback sensors 116 such as a current sensor or a hallsensor, one or more communication lines for transmitting signals and anamplifier 108.

In some examples, the control unit 102 can be in communication with theactuator 104. More specifically, the control unit 102 is capable oftransmitting, over the communication line, an electric current such as aPWM signal corresponding to the desired output position of the motor110, more specifically the position of the output shaft 112 (e.g., theoutput shaft of the gear segment, the final drive). The PWM signal canbe transmitted to the microcontroller 106 within the actuator system 100where the PWM signal can be converted to an operational motion to beoutput at the motor 110 to achieve the desired output position asindicated by sensor 116.

In some examples, once a desired output motor position is determined, atthe actuator 104, within an operational or executable positional rangeof the motor 110, a corresponding PWM command can be determined within aPWM range accordingly. In turn, the control unit 102 converts thecorresponding PWM command into a variable digital PWM signal that can beoutput using a PWM, otherwise described as a wave generator or a pulsegenerator, comprised within the control unit 102.

Actuator systems 100 commonly have one or more sensors or feedbacksensors 116 coupled to the actuator 104 or to the motor 110, e.g., suchas a hall sensor or a current sensor. Feedback sensors 116 are capableof communicating a feedback signal to the control unit 102 via themicrocontroller 106. The feedback sensor 116 may be capable of detectingdata in relation to the motor 110 or the gearset output shaft such as,for example, position data, diagnosis data or PWM signal errors.

In some examples, feedback data can be monitored at the control unit 102to determine an offset between the actual output position of the motorand the initial PWM command or the PWM signal transmitted to theactuator 104. In some examples, the feedback data can be used to adjust,correct the PWM signal when determining subsequent PWM commands in anattempt to compensate for any errors detected by the feedback sensor116. Error correction may be dynamic for example.

It shall be appreciated that there are many forms of feedback sensors116 or feedback control systems as well as many variations of pulsewidth modulating circuitry are readily available in the field ofelectromechanics for use in smart motor actuators 100 of describedexamples.

With reference to FIG. 2 , known methods of operating actuators,particularly smart motor actuators, will now be described. Morespecifically, FIG. 2 shows an example graph depicting the relationshipbetween the commanded output positions and the actual output positionsof the motor at each step in the PWM command range in conventionalsystems that employ a single gain level transfer function.

For the operation of actuators, the relationship between the desiredoutput motor position and its corresponding PWM command can be definedusing a transfer function. In conventional actuator systems, one lineartransfer function having a single gain level in the form y=mx+c isgenerally implemented, correlating the desired output position to therequired PWM command and vice versa.

Actuator motors tend to have an operational range of 0% and 100%,whereas, the PWM command commanding the PWM signal to be generated doesnot make use of the full range of commands that are available. Forexample, at the lower and upper limits of the PWM range, the PWM signalsproduced are indistinguishable from short to ground, short to battery,or open circuit, as it would be understood by the skilled person.

In operating actuator systems, the PWM command range is distributedevenly over the operational range of the actuator motor. Therefore, byimplementing a single gain transfer function, there may be inevitablyfewer 1% steps available as true operational positions than the full 0%to 100% operational range of the motor. This can create an offsetbetween the PWM command range and the operational range of the motor'sposition. Thus, in actuator systems, where for example the resolution ofthe PWM command is typically set at 1%, a 1% increase to the PWM commandtranslates to an increase greater than 1% to the output position of themotor.

The PWM command resolution is a function of a timer within themicrocontroller 106, which requires a resolution notably smaller than 1%in order to discriminate between each of the 1% PWM command steps. Thus,low cost microcontrollers tend to have a timer with channels of fewerbits resulting in limited resolution levels and may be unsuitable forapplications requiring high levels of accuracy. Whereas, in moreadvanced or higher quality microcontrollers, it may be possible toachieve a resolution of less than 1%.

In FIG. 2 , three variables are illustrated. Namely, the PWM commandssent at 1% resolution 202, corresponding commanded motor positions 204,and the output motor angles in degrees 206. In the example of FIG. 2 ,for example, the PWM only produces signals within a PWM command range of75%, from 12.5% to 87.5%, to control the operational output of themotor. In this example, the result is a gain level that is greater than1%, more specifically 1.333%. Putting this into context, for each 1%step in the PWM command range, the motor's output position is set toconsistently increase or decrease by 1.333% of its operational range.

In conventional methods, applying a single gain transfer function asdescribed in the example above results in limitations in the operationof actuator systems, mainly due to a lack of control over the motor. Thelimitation is specifically affected by the discontinuity wherein not allof the individual 1% steps or increments of the operational range of themotor are available as true operational outputs. E.g., in some portionsof the operational range of the motor, the discontinuity may result is anon-linear behavior in relation to the change in the motor's positionaloutput. Such systems may not be capable of reaching certain targetpositions accurately and may prove to be ineffective.

Due to the 1% resolution of the PWM command range, the output positionis likely to be either rounded down, up or simply truncated producingpositional gaps between subsequent positions that can be achieved by thesystem within the operational range of the motor. This is represented asripples in FIG. 2 , representing the lack of true operational outputpositions of the motor within its operational range due to the singlelinear transfer function as described above.

Furthermore, as shown in FIG. 3 , during the operation of actuatorsthere may be additional contributions of error or limitations. Oneexample of such contributions includes, e.g., signal losses as the PWMsignal is transmitted from the control unit to the microcontroller atthe actuator.

Illustration 300 shown in FIG. 3 shows an example where the edges of thePWM signal are seen to incur losses over time. This may be due to, e.g.,EMC capacitors at both ends of the communication line causinginaccuracies to the received PWM signal at the microcontroller, forexample, as the capacitance value drifts with temperature and time. Sucherrors may amount to an unwanted offset between the desired and actualoutput positions of the motor, which may result in an undesirable levelof noise.

Other parameters that might affect the operation of smart motoractuators may include, but is not limited to, e.g., further internalsignal losses, signal to noise ratio and size or cost of componentparts.

Single gain transfer functions are therefore only adequate in systemswhere precise control is not required or is not necessary, or if thelevel of control required is constant for complete and effectiveoperation, for example. For example, it may be the case thatmid-positional sub-ranges do not require accurate positioning of themotor and does not result in faults. However, this may not be the caseat more particular regions or sub-ranges, typically at end limits of thetransfer function, where inaccuracies in output motor positions may bedetrimental and may affect the operation of the actuator system.

In applications of high-performance motion control systems or those thatrequire a degree of precision or control for effective and reliableoperation, it is desirable to be able to achieve accurate levels ofpositional output using PWM commands. For some actuators, for examplegas valves, the last few steps of closure are critical and discontinuityin output motor positions caused by single gain transfer functions causedegraded control. For example, an exhaust butterfly valve used togenerate backpressure for exhaust gas recirculation in engine controlsystems has its' greatest effect just as it closes and therefore itwould be ideal to be able to achieve greater control over the closingpositions of the valve.

Such applications may require a linear or substantially linear gainlevel at particular regions or segments of the operational range of themotor, which is not possible using a single gain transfer function. Thiscan be particularly true for the lower and upper limits of theoperational range of the motor, where a valve requires careful openingand closing for example. In other applications, certain positions mayrequire acceleration or deceleration or may require a varied force to beapplied, for example. It can be said that conventional methods employingsingle gain level transfer functions are not suitable for suchapplications.

With reference to FIG. 4 , some examples of the present disclosure willnow be described. More particularly, FIG. 4 shows a graph illustratingan example piecewise transfer function depicting a change in thepositional output of the motor over the full range of PWM commands usingtwo gain levels.

Knowledge of system parameters and the impact of controlling suchparameters can be used as an indication as to which sections of thetransfer function should provide tighter control, for example. In thisway, a multi-gain transfer function can be used to develop systems andmethods of the present disclosure, and to overcome the shortcomings ofsingle gain methods and system.

More specifically, some examples implement a multi-gain transferfunction that defines two or more segments of distribution of the PWMcommand range and the operational range of the motor to determine thePWM signal that is required. By implementing a multi-gain transferfunction, the gain level may be set high for sub-ranges or portions ofthe operational range of the motor where the controlled actuator effectis not critical. Similarly, the gain level may be set to be low orsubstantially linear in regions or portions of the operational range ofthe motor where precise control is required.

In the example transfer function of FIG. 4 , the control range of 10% to90% can be split into two range segments requiring different levels ofcontrol. As shown in FIG. 4 , from PWM commands 10% to 65%, the actuatorposition gain level is 1.3636% for every 1% of the PWM command in movingthe valve position from 0% to 75%. This results in missed steps onlywhere accurate positions are not essential for the effective control ofthe valve. From 66% to 90% of the PWM command range, however, thestepwise movement of the motor can be 1% for every 1% PWM command inmoving the valve position from 76% to 100%, having a linear correlationand thus a great level of control in accessing all positions availablewithin the final 25% of the positional range of the valve. This resultsin a method capable of achieving all possible output motor positionsduring the critical phases of the motor. For example, the method maycomprise controlling the position of the valve over first range segmentusing a first linear transfer function and the position of the valveover second range segment using a second linear transfer function. Thefirst linear transfer function may correspond to valve positions from“open” to “˜75% closed” and the second linear transfer function maycorrespond to valve positions from “˜75% closed” to “closed”. Forexample, the first linear transfer function may be:

${{{Valve}\mspace{14mu}{{position}\mspace{14mu}\lbrack\%\rbrack}} = {\left( \frac{76}{56} \right)*\left( {{{PWM}\mspace{14mu}\lbrack\%\rbrack} - {10\mspace{14mu}\lbrack\%\rbrack}} \right)}},$and the second linear transfer function may be: Valve position[%]=PWM[%]+10[%].

In some examples, the piecewise transfer function may be determinedusing the following steps, by: acknowledging the operational range ofthe motor; acknowledging the PWM command range; determining one or moresub-ranges or segments of the operational range of the motor wheretighter control may be required; determining one or more gain levelsrequired at the determined sub-ranges where tighter control may berequired; applying the knowledge of the gain levels required andcorresponding sub-ranges in order to determine the distribution of thePWM command range over the operational range of the motor position;defining a piecewise transfer function having at least two differentgain levels, wherein the remaining operational range of the motor issubject to a gain level of that defined by the distribution.

With reference to FIG. 5 , a plotted view of the example implementationof the piecewise transfer function according FIG. 4 will now bedescribed. More particularly, FIG. 5 shows a graph 500 depicting therelationship between the commanded and actual output positions of themotor over the full range of PWM commands, using the piecewise transferfunction shown in FIG. 4 .

In FIG. 5 , three variables are illustrated. Namely, the PWM commandssent at 1% resolution 502, corresponding commanded motor positions 504,and the output motor angles in degrees 506. In this example, there is ahigh gain segment from 0% to 75% that can be seen to miss steps in thepositional range of the motor. Additionally, there is a low gain segmentfrom 76% to 100% depicting a linear gain level where accurate control ofthe system can be obtained.

In some examples, in order to achieve tighter control, the gain level ofthe PWM command to the actuator output position can be arranged to be aratio of 1:1, for example. Where it is acceptable for control can beless tight, a greater or higher gain level may be allowed in order toaccess the full range of positions operational by the motor, for exampleusing a ratio of 1.7:1. Commonly, the tight control of the motor may berequired at one end or both ends of the transfer function. If at bothends, for example, then the gain levels may be represented as a ratio of1:1 to 1.7:1 to 1:1 as the PWM command increases from its lowest value.

With reference to FIG. 6 shows an exploded view 600 of the operationalrange portion controlled by a linear gain level as shown in FIG. 5 .More specifically, this region depicts the linear relationship betweenthe commanded and actual output positions of the motor at each PWMcommand.

Examination of the commanded PWM positions shows linearity across thepositions of the motor output within said operational range portion. Inexample examples, the same transfer function in reverse can be usedprovide a closed loop control of the moveable element of the actuator.This allows for fine control that may be required, e.g., due tobackpressure in exhaust butterfly valves.

Actuator systems 100 often comprise feedback sensors 116 coupled to theactuator 104 or the motor 110 which are configured to transmit orcommunicate feedback data to the control unit 102. The feedback data,e.g., may relate to PWM modulation error, pose information of the motoror diagnosis data.

In some examples, the control unit 102 implementing a multi-gain leveltransfer function to output desired PWM signals may be capable ofaltering, correcting or adjusting the PWM signal in order to achieve thedesired motor positions efficiently and effectively. The adjustments maybe made dynamically or in substantially real-time for example. Thecontrol unit 102 may use feedback data received from the feedback sensorto determine whether to adjust the PWM signal in order to achieve thedesired output positions of the motor 110.

In some examples, the control unit 102 may compensate for signal errorsthat occur during the transmittance of PWM signals. In some examples,e.g., the signal corresponding to the actual output of the motor 110 canbe fed back to the control unit 102 where it can be superimposed orcompared to the initial PWM signal that was sent to drive the motor 110.In this way, the actuator system 100 may be able to compensate forerrors or offsets using subsequent PWM signals that are transmitted.

In some examples, the control unit 102 may be further capable ofaltering, correcting or adjusting the PWM signal based on one or morepredetermined logic conditions relating to feedback data and/or one ormore vehicle parameters. The control unit 102 may be configured toreceive feedback data and/or one or more vehicle parameters and assessthe variable data to determine the PWM signal.

Although FIG. 1 shows the example actuator control system 100 asincluding a number and configuration of individual components, in someexamples, any number of the components of system 100 may be combined,programmed to be in communication with, and/or integrated as modules forexample. The actuator system 100 may include component parts or moduleseach of which can be communicatively coupled to any suitablecommunication protocol or network.

In some examples, any suitable alternative communication line may beused for the communication between the control unit 102 and the actuator104, for example in order to transmit PWM signals from the control unit102 to the actuator 104 as well as receiving feedback data from thefeedback sensor 116 at the control unit 102. Some examples ofcommunication protocols that may be implemented as part of suchactuators 100 as described herein include, but is not limited to, singlewire PWM grounding protocols, standard CAN communication protocols orstandard LIN communication protocols, for example.

FIG. 7 shows a vehicle 700 comprising an actuator control system 702, inaccordance with some examples of the disclosure. In the example shown inFIG. 7 , the vehicle 700 comprises an engine 704, an exhaust system 706and actuator 708 configured to control the flow of exhaust gases throughthe exhaust system 706, e.g., by moving a moveable element of an exhaustgas flow valve. Control unit 710, e.g., microcontroller 106, is inoperable communication with engine 704, e.g., by virtue of an enginecontrol module, exhaust system 706, e.g., by virtue of an exhaustcontrol module, and actuator 708, e.g., by virtue of an actuator controlmodule. Control unit 710 is configured to carry out one or more of theabove disclosed methods to control a position of the moveable elementbased at least one of a first PWM signal or a second PWM signal, asdescribed above. Whilst the example shown in FIG. 7 relates tocontrolling the operation of a flow control valve of an exhaust system,it is to be understood that the present disclosure may relate to thecontrol and/or actuation of any appropriate moveable element, and inparticular, but not exclusively, to the control and/or actuation of amoveable element of a vehicular system, e.g., based upon one or moreoperational characteristics of the moveable element and/or the vehicle.

FIG. 8 shows an exemplary block diagram of control unit 710. Controlunit 710 includes storage 712, processing circuitry 714 and I/O path716. Control unit 710 may be based on any suitable processing circuitry.As referred to herein, processing circuitry should be understood to meancircuitry based on one or more microprocessors, microcontrollers,digital signal processors, programmable logic devices,field-programmable gate arrays (FPGAs), application-specific integratedcircuits (ASICs), etc., and may include a multi-core processor (e.g.,dual-core, quad-core, hexa-core, or any suitable number of cores). Insome examples, processing circuitry may be distributed across multipleseparate processors, for example, multiple of the same type ofprocessors (e.g., two Intel Core i9 processors) or multiple differentprocessors (e.g., an Intel Core i7 processor and an Intel Core i9processor).

Storage 712, and/or storages of other components of actuator controlsystem 702 may be an electronic storage device. As referred to herein,the phrase “electronic storage device” or “storage device” should beunderstood to mean any device for storing electronic data, computersoftware, or firmware, such as random-access memory, read-only memory,hard drives, and the like, and/or any combination of the same. In someexamples, control unit 710 executes instructions for an applicationstored in memory (e.g., storage 712). Specifically, control unit 710 maybe instructed by an application to perform the methods/functionsdiscussed herein.

Control unit 710 may be configured to transmit and/or receive data viaI/O path 716. For instance, I/O path 716 may include a communicationport(s) configured to transmit and/or receive data from at least one ofan engine control module, an actuator control module and a vehicularsystem control module, such as an exhaust system control module.

The disclosure of this invention is made for the purpose of illustratingthe general principles of the systems and processes discussed above andare intended to be illustrative rather than limiting. More generally,the above disclosure is meant to be exemplary and not limiting and thescope of the invention is best determined by reference to the appendedclaims. In other words, only the claims that follow are meant to setbounds as to what the present disclosure includes.

While the present disclosure is described with reference to particularexample applications, shall be appreciated that the invention is notlimited hereto. It will be apparent to those skilled in the art thatvarious modifications and improvements may be made without departingfrom the scope and spirit of the present invention. Those skilled in theart would appreciate that the actions of the processes discussed hereinmay be omitted, modified, combined, and/or rearranged, and anyadditional actions may be performed without departing from the scope ofthe invention.

Any system feature as described herein may also be provided as a methodfeature and vice versa. As used herein, means plus function features maybe expressed alternatively in terms of their corresponding structure. Itshall be further appreciated that the systems and/or methods describedabove may be applied to, or used in accordance with, other systemsand/or methods.

Any feature in one aspect may be applied to other aspects, in anyappropriate combination. In particular, method aspects may be applied tosystem aspects, and vice versa. Furthermore, any, some and/or allfeatures in one aspect can be applied to any, some and/or all featuresin any other aspect, in any appropriate combination.

It should also be appreciated that particular combinations of thevarious features described and defined in any aspects can be implementedand/or supplied and/or used independently.

The invention claimed is:
 1. A method of operating an actuator forpositioning a movable element, the method comprising: determiningoperational characteristics of the movable element over its operationalrange of motion; generating a first PWM signal to control the actuatorover a first portion of the operational range of motion of the movableelement; generating a second PWM signal to control the actuator over asecond portion of the operational range of motion of the movableelement, wherein: the first PWM signal is based on a linear transferfunction having a first gain level and the second PWM signal is based ona linear transfer function having a second gain level, and the firstportion of the operational range of motion requires a lower degree ofaccuracy than the second portion of the operational range of motion;executing an output position of the movable element based the first PWMsignal or the second PWM signal; and determining a distribution of apiecewise linear transfer function, the distribution describing: (a) thefirst gain level over the first portion of the operational range ofmotion, (b) the second gain level over the second portion of theoperational range of motion, and (c) the remaining operational range ofmotion of the movable element is subject to a third gain level of thatdefined by the distribution.
 2. The method of claim 1, wherein the firstPWM signal is generated based on the determined operationalcharacteristics of the movable element at the first portion of itsoperational range of motion and the second PWM signal is generated basedon the determined operational characteristics of the movable element atthe second portion of its operational range of motion.
 3. The method ofclaim 1, wherein the first gain level and the second gain level eachindicate a ratio between the operational range of motion of the movableelement and a PWM range.
 4. The method of claim 1, wherein at least oneof the first PWM signal and the second PWM signal is further generatedto control the actuator over one or more additional portions of theoperational range of motion of the movable element.
 5. The method ofclaim 1, wherein the first gain level is greater than 1 and the secondgain level is equal to
 1. 6. The method of claim 1, further comprising astep of receiving feedback data in relation to the movable element'sposition from a feedback sensor coupled to the actuator.
 7. The methodof claim 6, further comprising a step of adjusting at least one of thefirst PWM signal and the second PWM signal in response to the feedbackdata.
 8. The method of claim 7, wherein the step of adjusting the atleast one of the first PWM signal and second PWM signal is based on oneor more vehicle parameters.
 9. An actuator control system comprising acontrol unit in operable communication with an actuator for positioninga movable element, the control unit being configured to: determine oneor more operational characteristics of the movable element over itsoperational range of motion; generate a first PWM signal to control theactuator over a first portion of the operational range of motion of themovable element; generate a second PWM signal to control the actuatorover a second portion of the operational range of motion of the movableelement, wherein: the first PWM signal is based on a linear transferfunction having a first gain level and the second PWM signal is based ona linear transfer function having a second gain level, and the firstportion of the operational range of motion requires a lower degree ofaccuracy than the second portion of the operational range of motion; andexecute an output position of the movable element based the first PWMsignal or the second PWM signal; and determining a distribution of apiecewise linear transfer function, the distribution describing: (a) thefirst gain level over the first portion of the operational range ofmotion, (b) the second gain level over the second portion of theoperational range of motion, and (c) the remaining operational range ofmotion of the movable element is subject to a third gain level of thatdefined by the distribution.
 10. The actuator control system of claim 9,wherein the control unit is configured to generate the first PWM signalbased on the determined operational characteristics of the movableelement at the first portion of its operational range of motion and thesecond PWM signal based on the determined operational characteristics ofthe movable element at the second portion of its operational range ofmotion.
 11. The actuator control system of claim 9, wherein the firstgain level and the second gain level each indicate a ratio between theoperational range of motion of the movable element and a PWM range. 12.The actuator control system of claim 9, wherein the control unit isconfigured to generate at least one of the first PWM signal and thesecond PWM signal to control the actuator over one or more additionalportions of the operational range of motion of the movable element. 13.The actuator control system of claim 9, wherein the first gain level isgreater than 1 and the second gain level is equal to
 1. 14. The actuatorcontrol system of claim 9, wherein the control unit is configured toreceive feedback data in relation to the movable element's position froma feedback sensor coupled to the actuator.
 15. The actuator controlsystem of claim 14, wherein the control unit is configured to adjust atleast one of the first PWM signal and the second PWM signal in responseto the feedback data.
 16. A vehicle comprising the actuator controlsystem of claim
 9. 17. The vehicle of claim 16, comprising means foradjusting at least one of the first PWM signal and second PWM signalbased on one or more vehicle parameters.
 18. A non-transitory computerreadable medium having instructions encoded thereon that when executedby control circuitry cause the control circuitry to: determineoperational characteristics of the movable element over its operationalrange of motion; generate a first PWM signal to control an actuator overa first portion of the operational range of motion of the movableelement; generate a second PWM signal to control the actuator over asecond portion of the operational range of motion of the movableelement, wherein: the first PWM signal is based on a linear transferfunction having a first gain level and the second PWM signal is based ona linear transfer function having a second gain level, and the firstportion of the operational range of motion requires a lower degree ofaccuracy than the second portion of the operational range of motion;execute an output position of the movable element based the first PWMsignal or the second PWM signal; and determine a distribution of apiecewise linear transfer function, the distribution describing: (a) thefirst gain level over the first portion of the operational range ofmotion, (b) the second gain level over of the second portion of theoperational range of motion, and (c) the remaining operational range ofmotion of the movable element is subject to a third gain level of thatdefined by the distribution.